The gigantic rocks of Meteora are perched above the town of Kalambaka, at a maximum height of 400 m (1200 ft). The most interesting summits are decorated with historical monasteries, included in the World Heritage List of Unesco. Only 6 of them have made it through the centuries, from an initial estimated number of 24. Mostly dating to the 14th and until the 16th century, these monasteries were built by monks who were previously hermits in the area, living in individual caves. Once united, these monks took months and years to carry the construction material to the top of rocks, using ropes, folding ladders, nets and baskets, and with much determination.